The paranasal sinuses are cavities inside the facial bones surrounding the nose, which communicate with the nasal cavity through narrow ostia. The mucous membrane of the sinus is continuous with that of the nasal cavity. The maxillary sinuses constitute the largest of these cavities. An opening in the medial wall of the maxillary sinus communicates with the middle meatus of the nose. Obstruction of the sinus ostium is a central event in the pathogenesis of sinusitis.
The gas nitric oxide (NO) is released in the human respiratory tract. The major part of the NO found in exhaled air originates in the nasal airways and this NO can be measured non-invasively with different sampling techniques. It is known that a large production of NO takes place in the parnasal sinuses where an inducible NO synthase is constantly expressed in the epithelial cells. NO is released also from other sources in the nose e.g. the nasal mucosa. However, the relative contribution from the different NO sources in the upper airways to the NO found in nasal air is difficult to estimate. The sinuses communicate with the nasal cavity through ostia and the rate of gas exchange between these cavities is dependent e.g. on the size of the ostia A patent ostium is essential for maintenance of sinus integrity. Blockage of the ostium, e.g. caused by virus-induced mucosal swelling, results in decreased oxygen tension, mucosal edema, reduced mucociliary transport and eventually bacterial colonisation. Earlier studies have shown that nasal NO levels are markedly decreased in airway disorders affecting the sinuses, e.g. primary ciliary dyskinesia (PCD) and cystic fibrosis (CF). The concentrations of NO in the healthy sinuses are very high, sometimes more than 20 ppm.
Sinusitis is a very common disease causing much human suffering and enormous costs for the society. The self-reported prevalence of chronic sinusitis in the USA is about 12% of the population. There are several problems involved in the diagnosis and treatment of this disorder. For example, headache, rhinorrhea and nasal congestion are extremely common, but these symptoms do not necessarily imply sinusitis. Therefore the true incidence of sinusitis is lower.
Proper ventilation of the sinuses is essential for sinus integrity. In fact, occlusion of the ostia is considered the key factor in the pathogenesis of sinusitis. Such occlusion may be of mechanical or mucosal origin i.e. septum deviation, nasal polyposis, allergic rhinitis or most commonly an acute viral infection. The basic principles of treatment are to cure any infection present and to promote sinus drainage both during and after treatment to prevent recurrence. Antibiotics remain the cornerstone treatment in medical handling of acute infectious sinusitis. In addition, medical intervention with nasal decongestants as well as surgical treatment is frequently used in prevention and treatment of chronic sinusitis with the purpose of improving sinus drainage.